Tanja Wolfsberger

Landfill mining in Austria: Foundations for an integrated ecological and economic assessment

For the first time, basic technical and economic studies for landfill mining are being carried out in Austria on the basis of a pilot project. An important goal of these studies is the collection of elementary data as the basis for an integrated ecological and economic assessment of landfill mining projects with regard to their feasibility. For this purpose, economic, ecological, technical, organizational, as well as political and legal influencing factors are identified and extensively studied in the article. An important aspect is the mutual influence of the factors on each other, as this can significantly affect the development of an integrated assessment system. In addition to the influencing factors, the definition of the spatial and temporal system boundaries is crucial for further investigations. Among others, the quality and quantity of recovered waste materials, temporal fluctuations or developments in prices of secondary raw material and fuels attainable in the markets, and time and duration of dumping, play a crucial role. Based on the investigations, the spatial system boundary is defined in as much as all the necessary process steps, from landfill mining, preparing and sorting to providing a marketable material/product by the landfill operator, are taken into account. No general accepted definition can be made for the temporal system boundary because the different time-related influencing factors necessitate an individual project-specific determination and adaptation to the facts of the on-site landfill mining project.

Landfill mining: Resource potential of Austrian landfills – Evaluation and quality assessment of recovered municipal solid waste by chemical analyses

Since the need for raw materials in countries undergoing industrialisation (like China) is rising, the availability of metal and fossil fuel energy resources (like ores or coal) has changed in recent years. Landfill sites can contain considerable amounts of recyclables and energy-recoverable materials, therefore, landfill mining is an option for exploiting dumped secondary raw materials, saving primary sources. For the purposes of this article, two sanitary landfill sites have been chosen for obtaining actual data to determine the resource potential of Austrian landfills. To evaluate how pretreating waste before disposal affects the resource potential of landfills, the first landfill site has been selected because it has received untreated waste, whereas mechanically–biologically treated waste was dumped in the second. The scope of this investigation comprised: (1) waste characterisation by sorting analyses of recovered waste; and (2) chemical analyses of specific waste fractions for quality assessment regarding potential energy recovery by using it as solid recovered fuels. The content of eight heavy metals and the net calorific values were determined for the chemical characterisation tests.

Landfill mining: Development of a cost simulation model.

Landfill mining permits recovering secondary raw materials from landfills. Whether this purpose is economically feasible, however, is a matter of various aspects. One is the amount of recoverable secondary raw material (like metals) that can be exploited with a profit. Other influences are the costs for excavation, for processing the waste at the landfill site and for paying charges on the secondary disposal of waste. Depending on the objectives of a landfill mining project (like the recovery of a ferrous and/or a calorific fraction) these expenses and revenues are difficult to assess in advance. This situation complicates any previous assessment of the economic feasibility and is the reason why many landfills that might be suitable for landfill mining are continuingly operated as active landfills, generating aftercare costs and leaving potential hazards to later generations. This article presents a newly developed simulation model for landfill mining projects. It permits identifying the quantities and qualities of output flows that can be recovered by mining and by mobile on-site processing of the waste based on treatment equipment selected by the landfill operator. Thus, charges for disposal and expected revenues from secondary raw materials can be assessed. Furthermore, investment, personnel, operation, servicing and insurance costs are assessed and displayed, based on the selected mobile processing procedure and its throughput, among other things. For clarity, the simulation model is described in this article using the example of a real Austrian sanitary landfill.

Landfill mining: Development of a theoretical method for a preliminary estimate of the raw material potential of landfill sites.

In recent years, the rising need for raw materials by emerging economies (e.g. China) has led to a change in the availability of certain primary raw materials, such as ores or coal. The accompanying rising demand for secondary raw materials as possible substitutes for primary resources, the soaring prices and the global lack of specific (e.g. metallic) raw materials pique the interest of science and economy to consider landfills as possible secondary sources of raw materials. These sites often contain substantial amounts of materials that can be potentially utilised materially or energetically. To investigate the raw material potential of a landfill, boreholes and excavations, as well as subsequent hand sorting have proven quite successful. These procedures, however, are expensive and time consuming as they frequently require extensive construction measures on the landfill body or waste mass. For this reason, this article introduces a newly developed, affordable, theoretical method for the estimation of landfill contents. The article summarises the individual calculation steps of the method and demonstrates this using the example of a selected Austrian sanitary landfill. To assess the practicality and plausibility, the mathematically determined raw material potential is compared with the actual results from experimental studies of excavated waste from the same landfill (actual raw material potential).

Landfill mining: Developing a comprehensive assessment method

In Austria, the first basic technological and economic examinations of mass-waste landfills with the purpose to recover secondary raw materials have been carried out by the ‘LAMIS – Landfill Mining Österreich’ pilot project. A main focus of its research, and the subject of this article, is the first conceptual design of a comprehensive assessment method for landfill mining plans, including not only monetary factors (like costs and proceeds) but also non-monetary ones, such as the concerns of adjoining owners or the environmental impact. Detailed reviews of references, the identification of influences and system boundaries to be included in planning landfill mining, several expert workshops and talks with landfill operators have been performed followed by a division of the whole assessment method into preliminary and main assessment. Preliminary assessment is carried out with a questionnaire to rate juridical feasibility, the risk and the expenditure of a landfill mining project. The results of this questionnaire are compiled in a portfolio chart that is used to recommend, or not, further assessment. If a detailed main assessment is recommended, defined economic criteria are rated by net present value calculations, while ecological and socio-economic criteria are examined in a utility analysis and then transferred into a utility-net present value chart. If this chart does not support making a definite statement on the feasibility of the project, the results must be further examined in a cost-effectiveness analysis. Here, the benefit of the particular landfill mining project per capital unit (utility-net present value ratio) is determined to make a final distinct statement on the general benefit of a landfill mining project.

Holistic assessment of a landfill mining pilot project in Austria: Methodology and application.

Basic technical and economic examinations of Austrian mass waste landfills, concerning the recovery of secondary raw materials, have been carried out by the ‘LAMIS – Landfill Mining Austria’ pilot project for the first time in Austria. A main focus of the research – the subject of this article – was the first devotion of a pilot landfill to an integrated ecological and economic assessment so that its feasibility could be verified before a landfill mining project commenced. A Styrian mass waste landfill had been chosen for this purpose that had been put into operation in 1979 and received mechanically–biologically pre-treated municipal waste till 2012. The whole assessment procedure was divided into preliminary and main assessment phases to evaluate the general suitability of a landfill mining project with little financial and human resource expense. A portfolio chart, based on a questionnaire, was created for the preliminary assessment that, as a result, has provided a recommendation for subsequent investigation – the main assessment phase. In this case, specific economic criteria were assessed by net present value calculation, while ecological or socio-economic criteria were rated by utility analysis, transferring the result into a utility–net present value chart. In the case of the examined pilot landfill, assessing the landfill mining project produced a higher utility but a lower net present value than a landfill leaving-in for aftercare. Since no clearly preferable scenario could be identified this way, a cost–revenue analysis was carried out in addition that determined a dimensionless ratio: the ‘utility – net present value quotient’ of both scenarios. Comparing this quotient showed unmistakably that in the overall assessment, ‘leaving the landfill in aftercare’ was preferable to a ‘landfill mining project’ in that specific case.